Flat Panel Radiators

I plan to replace two cast iron radiators with Runtal flat panel radiators; one on the first floor and one directly above on the second floor. The existing hot water system has black iron pipe. What is the best way to connect new 1/2" copper for the flat panels into the black iron pipe? There is one set of Tees already connected to the supply and return lines for the existing first floor radiator. The second floor is a new room.

These threaded connections? If so, I'd screw in a brass nipple, then transition to the copper. The pros may have a better way.

Adding a second panel, especially on a second floor, will probably mean you need to deal with balancing the flow...the lower one will get more heat since it will be harder to push enough flow up another flight. You may need some additional controls/valves to ensure both get enough flow to warm the rooms evenly.